Saline and Sodic Soils in Wisconsin: The Sad Story of an ... · The Sad Story of an Infiltration Pond for Waukesha County Storm Water Workshop 14 Mar 2012 Kyle Rudersdorf, David Evans,

Saline and Sodic Soils in Wisconsin: The Sad Story of an Infiltration Pond

for Waukesha County Storm Water Workshop 14 Mar 2012

Kyle Rudersdorf, David Evans, Glen Obear, Shane Griffith, Mackenzie Naber and Chris Long

under the supervision of

Phillip Barak, PhDProfessor, Dept of Soil Science

University of [email protected]

and with the sponsorship of The City of Middleton and the site owner

$10.5 millionOpened Aug 2008

~153,000 sq. ft. bldg~440,000 sq. ft. parking lot3 Stormwater quality basins:

2300, 8000 & 8700 sq. ft.(~30:1 impermeable:basins)

Madison & Dane Co. Public Health ROAD SALT REPORT – 2008/09 http://www.publichealthmdc.com/publications/documents/RoadSalt2009.pdf

Tons of salt applied or purchased by municipality, winter of 2008/9:27,000 Dane Co.9,000 City of Madison1,150 Town of Burke1,350 City of Middleton2,700 Others

Annual Madison salt application:10 – 25 tons/mile (Goal: 6 tons/mile)

Diagnostic techniques:

Salinity—

• Electrical conductivity (EC) of soil water or saturated soil extract (lab; dS/m or mmho/cm)

• portable electromagnetic (EM) soil conductivity sensor mounted on vehicle (field)

Sodicity—

• Measurement of Exchangeable Sodium Percentage (ESP) by cation displacement

• Measurement of Sodium Adsorption Ratio (SAR) in soil solution, saturated soil extract or irrigation water

Quirk and Schofield. 1957. J. Soil Science

Sampling at retention ponds, Aug 2010

Collection of cores from retention ponds (in background).

Bulk Density, Mg m-3

1.0 1.2 1.4 1.6 1.8 2.0

Dep

th,

cm

0

5

10

15

20

25

4N vs Depth

3E vs Depth

Dispersion of 1-cm core segments in 1% sodium polymetaphosphate and mechanical agitation, here allowed to settle showing bands of sand, silt and suspended clay, for particle size determination by laser scattering—after removal of pea gravel by sieving.

Particle Size Distribution by Laser Scattering, gravel removed. Gravel was 10-15% of core segment, by wt.

Exchangeable Sodium Percentage

0 5 10 15 20 25 30 35

Dep

th,

cm

0

5

10

15

20

25

4N

3E

Typical remediation techniques:

Saline soils—Add high quality water and drain

Sodic and saline-sodic soils—Add gypsum, CaSO4·2H2O, and then drain

(Gypsum dissolves to provide a relatively high ionic concentration and provides Ca2+ to displace exchangeable Na+)

Contraindicated—adding high quality water and draining; likely to cause impermeability

Quirk and Schofield. 1957. J. Soil Science

Findings for a different West Madison retention pond, for which change in SAR and EC upon gypsum addition were calculated.

(Note persistence of high SAR and EC until May.)

Gypsum Added

Pond Water Characteristics: Gypsum Added9/1/200x 1/27/200x 5/12/200x

--mM-- SAR EC* SAR EC SAR EC --g/L--

0 0.9 0.1 11.7 1.2 11.6 1.0 0

5 0.2 1.3 4.8 2.4 4.3 2.2 0.9

10 0.2 2.3 3.5 3.4 3.2 3.2 1.7

Sat’d 0.1 3.1 2.9 4.4 2.6 4.2 2.6

* dS/m or mmho/cm

Falling head permeameterto measure Ksat on intact cores, using sequence of:

•tap water, •gypsum-saturated water, and •25 mM calcium chloride

cm d-1 cm h-1 cm s-1

Sand 504 21.0 5.83E-03

Sandy loam 62.6 2.59 7.19E-04

Loam 31.7 1.32 3.67E-04

Silt loam 16.3 0.68 1.89E-04

Clay 1.44 0.06 1.67E-05

Core 2E:

tapwater 0.33 0.01 3.86E-06

gypsum-sat’d 2.32 0.09 2.69E-05

25 mM CaCl2 2.35 0.10 2.72E-05

250 mM CaCl2 2.53 0.10 2.93E-05

Core 2N:

tapwater 0.52 0.02 6.06E-06

gypsum-sat’d 0.72 0.03 8.30E-06

Ksat measured with Falling Head Permeameters

Conclusions:

•This is an autopsy, not a resuscitation or remediation

• Engineered soil has puddled and structure has been lost

•Most of runoff water exits directly thru overflow pipes to sewers

•Retention ponds will never be able to remediate salts but will only pass it on, sooner or later, to groundwater or overflow drains

Replacing the soil of the ‘storm water quality basins’, which failed in two winters, should be accompanied by:

•Diversion of sodium chloride used for deicing parking lot, creating a ‘3-season basin’

•Routine addition of gypsum to ponds to raise SAR and reduce tendency to form sodicsoil (~2 g/L)

•Substitution of calcium chloride, calcium acetate, or potassium chloride for sodium chloride in parking lots draining into retention ponds will prevent occurrence of clogging due to sodicity

•Rating of engineered soils for sensitivity to sodicity if no change from sodium chloride is feasible.

Engineered soil, sand, <5% clay

Sandy engineered soil:

Preliminary Conclusions/Questions re: sandy engineered soil:

• Hydraulic conductivity can be cut in half by sodicity; more to come later?

• More resilient to salt than engineered soil currently used in these ponds

• Sandy soil still bleeds clay when sodic; will this lead to impermeability over time if a clay lamellae forms?

• Would not something other than sodium chloride be desirable?

• How about something other than a swelling clay, such as attapulgite or biochar, to form a moisture retentive upper horizon for plant growth?